Water Ozonation and Bioremediation System and Associated Methods

ABSTRACT

A method of treating water includes exposing influent comprising water desired to be treated to ozone in sufficient quantity to disrupt cell walls of undesired microorganisms therein, thereby releasing nutrients from within the microorganisms in a form amenable to bioassimilation. The ozone is further in sufficient quantity to oxidize toxic, humic substances to a form amenable to plant bioassimilation. Aquatic plants are contacted with the ozone-exposed water, the aquatic plants being adapted to remove the released and oxidized nutrients therefrom. Water emerging from the aquatic plants is then again exposed to ozone in sufficient quantity to further purify the water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/930,699,filed Aug. 31, 2004, now issued U.S. Pat. No. 7,014,767, which is acontinuation of application Ser. No. 10/376,921, filed on Feb. 27, 2003,now issued U.S. Pat. No. 6,783,676, which itself claimed priority toprovisional patent application Ser. No. 60/361,632, filed on Feb. 28,2002.

FIELD OF INVENTION

The present invention generally relates to water purification systemsand methods, and, in particular, to such systems and methods for using acombination of ozonation and bioremediation to achieve at least partialpurification.

BACKGROUND

Algae comprise a group of aquatic plants with over 18,000 species andthere are many times more aquatic plants growing rooted to the bottomand attached to other plants, floating and a mixture of both. As withterrestrial plants, the primary nutrients carbon, nitrogen andphosphorus, as well as a suite of micronutrients are essential forgrowth. Algae have developed the ability to exist where nutrients are invery short supply through many complex and unique biological pathways.

The removal of carbon, nitrogen, phosphorus, and the micronutrients hasbecome key to improving the quality of polluted water and restoringecological balance. It is widely known that many aquatic plants absorbmetals beyond their immediate needs, thus bio-concentrating them withinplant cells as they remove them from water. Algae and other aquaticplants can take up primary and micronutrients that may be inoverabundance, such as carbon, nitrogen, phosphorus, potassium, iron,aluminum, calcium, and other substances and thus can be utilized toremediate an ecosystem. One embodiment for achieving such bioremediationcomprises attached algae; in other embodiments any aquatic plant may beused for nutrient uptake that extracts its nutrients from the water.

Bioremediation can occur when water flows over stationary algae orperiphyton which, like all plants, require carbon. Periphyton has ahigher productivity than any terrestrial plant. As modeled in thepartial pressure of gas laws this creates significant consumption ofcarbon dioxide. Conservatively, 20 times more CO₂ (in the form ofbicarbonate) is absorbed by periphyton as is absorbed by a mature forestland on an equal area. Significantly higher cell productivity ofperiphyton greatly affects O₂ production producing many times more O₂per unit area.

Water remediation by regularly harvested periphyton has been shown to be50 to 1000 times higher than constructed wetland systems per unit area.Remediation can occur when water flows over stationary algae taking upmacro nutrients (carbon, nitrogen and phosphorus) and micro nutrients,while discharging oxygen as high as three times saturation. This highoxygen and hydroxyl environment has shown to reduce organic sediments by0.25 meters per year. In long runs periphyton have been shown toincrease pH due to carbon uptake to as high as 11. Filtration can occurthrough adsorption, absorption, physical trapping, and other morecomplex means.

A system used to effect this uptake is known as a “periphyton filter,”the periphyton comprising a culture of a family of fresh, brackish,and/or salt water plants known as “attached algae.” Unlike suchorganisms as free-floating plankton, benthos or attached algae are astationary community of epiphytes that will grow on a wide variety ofsurfaces. When occurring in the path of flowing water, the stationaryalgae and associated organisms remove nutrients and othercompounds fromthe passing water, while absorbing carbon dioxide and releasing oxygenas a result of respiration, in turn a result of photosynthesis. Once analgal colony or community is established, roots or holdfasts cover theculture surface. If the plant bodies are harvested, leaving the rootsbehind, the nutrients and other pollutants contained in the plant bodiesare removed from the water. Trapped in and around plant biomassnutrients can be exported continuously from a water stream, causing anatural filtration effect.

A further advantage to this technique is that the enriched algae can beharvested and used as a fish or animal feed or as another type of fibersource, which serves to return the nutrients to the food chain.

Studies in algal turf and periphyton filtration are known in the art.Algal turf techniques have been disclosed in Adey's U.S. Pat. No.4,333,263, and the present inventor's U.S. Pat. Nos. 5,131,820;5,527,456; 5,573,669; 5,591,341; 5,846,423; and 5,985,147, thedisclosures of which are incorporated hereinto by reference.

Periphyton filters (PF) have potential for use in a variety ofapplications. For example, the periphyton can be used to replacebiological or bacterial filters in aquaria as pioneered by Stork anddeveloped byAdey. As mentioned, natural periphyton can be used to removenutrients and other contaminants from polluted waters. In addition, byharvesting the algal mass, various processes can be used to produce abiomass energy source such as methane or ethanol, fertilizer, a human oranimal food additive or supplement, cosmetics, or pharmaceuticals.

The high productivity of the algae in a fibrous form has also yieldeduses in the paper and paper products industry, as the harvested algaeare many times stronger and easier to process than wood fiber. Thelimiting factor in many paper production lines is wet strength. Algalfibers can have exceptional wet strength, which can enhance paperproduction rates while removing nutrients from the paper plant wastestream thus enhancing the environmental preferability of a product. Mostpaper plants produce high-nutrient waste streams which can be greatlyenhanced by periphyton culture systems while producing cleaner wateroutflow and fiber which can be used to enhance the products manufacturedby the plant. This capability has resulted in an economically, socially,and environmentally sustainable method of managing human impact onaquatic ecosystems.

Aquatic plants can be used for hydroseeding, concrete form liners,plaster form liners, ceiling tiles, moldings, architectural details andornaments, paper backing for gypsum board, building panels, molded pulppackaging, agricultural pots and planters, erosion control products,body panels, and other items.

Triatomic oxygen or O₃ (ozone) is a naturally occurring gas created bythe force of corona discharge during lightning storms or by UV lightfrom the sun. O₃ occurs in an upper atmospheric layer and is critical tothe temperature balance on Earth.

O₃ in the lower atmosphere is viewed as a pollutant; however, man-madeO₃ systems are fitted with simple destruction technology that completelyeliminates concerns about O₃ use by man. Such systems are widely usedfor drinking and wastewater treatment as well as air filtration withdoses bearing healthy safety factors.

O₃ is 1.5 times as dense as oxygen and 12.5 times more soluble in waterand at high doses leaves substantially no residuals or byproducts exceptoxygen and a minimal amount of carbon dioxide, trace elements, andwater. It can be manufactured from dry air or from oxygen by passingthese gases through an electric field of high potential sufficient togenerate a corona discharge between the electrodes. This coronadischarge is just under the energy level of an automotive spark plug.Ultraviolet light and shorter-wavelength radiation also causes oxygen toundergo conversion to O₃, which may be used for industrial wastewaters(Belew, 1969). O₃ is a more potent germicide than hypochlorous acid byfactors of 10—100-fold and disinfects 3125 times faster than chlorine(Nobel, 1980).

O₃ is highly unstable and must be generated on site. The measure of anoxidizer and its ability to oxidize organic and inorganic material isits oxidation potential (measured in volts of electrical energy). Theoxidation potential of O₃ (−2.07 V) is greater than that of hypochlorousacid (−1.49 V) or chlorine (−1.36 V), the latter agents being widelyused in water treatment practice at present.

SUMMARY OF THE INVENTION

The present invention relates to systems and methods for improving waterquality, and, more particularly, to such systems and methods forbioremediating water with an attached algal colony or other aquaticplants and, most particularly, to treating water against toxiccompounds, microorganisms, and other water-borne pollutants in concertwith an attached algal colony or other aquatic plants in concert withintroduction of ozone (O₃) into the water to be treated.

A residence time is required for the ozone gas in the water to contactand oxidize substances therein. Typically this is done with large mixingchambers and mixing pumps. Many times the site of a periphyton filter issome distance from the water to be treated. With mixing occurring justdownstream of the supply pump or pipe entrance at single or multiplestatic mixers, integration can be included in the pipe and then theresidence time in the pipe allows for treatment as the water travels tothe periphyton filter. This extended contact time can provide increasedtreatment. Multiple static mixers and ozone injection points may beemployed for optimum efficiency. Economical covered ponds can also beused to increase contact time.

Pumping water down a feed tube within a larger fully encased well with aclosed bottom and then injecting ozone at the bottom of the well, wherethe pressure is at maximum, may also enable better dispersion in thewater column. As the water rises up the well, necessary contact time isprovided between the ozone and substances in the water.

As set forth in the present invention, combining ozone and periphytonfiltration provides many advantages over use of either technologicalapproach separately. Ozone breaks down cells to release bound nutrientsinto the water, preparing them for fast uptake by periphyton.Treatability studies on the phenomenon have been executed on severalCentral Florida lakes. Lake Apopka, for example, has a very highstanding crop of phytoplankton. At the east side of Lake Apopka, watermeasures 2 ppb SRP (soluble reactive phosphorus) and 352 ppb TP (totalphosphorus). After a 1 mg/l dose ozone was applied to this water the SRPwas raised to 147 ppb. The rise in reactive nutrients provides superiorwater for aquatic plant culture and an improvement in water quality.This is largely due to the oxidation of plankton and bacteria cell wallsand the spilling of those cells' cytoplasm, containing reactivenutrients, into the water.

Toxic cyanobacteria pose a particularly challenging set of eliminationchallenges in that the toxins may exist both inside and outside thealgal cell. While ozone can be used to detoxify such substances in bothcases, the periphyton filter also has a detoxifying capability. As thepresent inventor described in U.S. Pat. Nos. 5,527,456; 5,573,669; and5,591,341, water passing across attached algal cultures experienced anincrease in pH owing to the removal of significant quantities of carbonby the algae. Algae remove carbon, nitrogen, and phosphorus as amacronutrients and many other elements and compounds as micronutrients.The removal of carbon, a mild acid, causes a rise in the number of (OH+)hydroxyl ions, as typically measured logarithmically as a rise in pH.This environment is aggressive to other compounds such as the algaltoxins released by cyanobacteria. Thus a synergistic combination ofozone pre- and post-treatment, to destroy toxins and make availablebound nutrients for periphyton along with periphyton to produce ahostile environment via production of hydroxyl ions, work together toboth detoxify and denutrify source waters.

Recirculation loops within combined systems can enhance water treatmentbecause the ozonation process is enhanced in waters with increased pH.In this embodiment water that has experienced an increase in pH via aperiphyton filter or other plant filtration system can then be exposedto ozonation with enhanced effectiveness owing to the pH increasemediated by aquatic plants.

Carbon that has been activated can bind toxins and other substances.Even further, ultraviolet light can be used to reduce all ozone ineffluent to preclude oxidation of aquatic plants. After water has beentreated by ozone and periphyton filtration, activated carbon can be usedto polish the water.

Ozone used prior to, during, and after filtration using periphyton andother aquatic plants has several synergistic effects.

1. Ozone breaks up planktonic algae in lake waters, making the nutrientsavailable for growth of periphyton and removal from water.

2. After the nutrients are available and removed by the periphyton, thewater can be returned to the water body in such a state that toxic algaecannot re-grow, thus effecting enhanced remediation.

3. Ozone destroys certain forms of toxic compounds found incyanobacteria (blue-green algae), recently found to be dangerous tohumans and other animals. These toxic compounds as well as the non-toxiccompounds are then available for incorporation into filamentous algaegrown for use in industries such as the paper products industry.

4. Ozone destroys both micro-invertebrates and their eggs, which oftensettle, hatch, and grow as they consume desirable periphyton,discharging nutrients and reducing the effects of filtration.

5. Use of innovative static mixing technology can be implemented such asthat used by Westfall and KOMAX corporations.

6. Use of covered ponds and supply pipes for increased ozone contacttime.

7. Use of chased wells for ozone injection provides enhanced ozonetreatment due to higher pressure at the well bottom.

8. Periphyton filtration and ozone in sequence or with recirculation canprovide enhanced treatment by enhanced pH/ozone performance.

9. Activated carbon filtration for post-treatment polishing of ozoneperiphyton treated water.

These treatment steps described herein can be used prior to aquiferrecharge and storage.

The features that characterize the invention, both as to organizationand method of operation, together with further objects and advantagesthereof, will be better understood from the following description usedin conjunction with the accompanying drawing. It is to be expresslyunderstood that the drawing is for the purpose of illustration anddescription and is not intended as a definition of the limits of theinvention. These and other objects attained, and advantages offered, bythe present invention will become more fully apparent as the descriptionthat now follows is read in conjunction with the accompanying drawing.

The features that characterize the invention, both as to organizationand method of operation, together with further objects and advantagesthereof, will be better understood from the following description usedin conjunction with the accompanying drawing. It is to be expresslyunderstood that the drawing is for the purpose of illustration anddescription and is not intended as a definition of the limits of theinvention. These and other objects attained and advantages offered, bythe present invention will become more fully apparent as the descriptionthat now follows is read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side cutaway view of an ozone contact chamber which may beemployed to treat large flows; and

FIG. 2 is a schematic diagram of a water treatment train combining ozoneand periphyton filtration in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A description of the preferred embodiments of the present invention willnow be presented with reference to FIGS. 1 and 2.

Referring to FIG. 1, an economical and efficient ozone contact chamberparticularly suited to large-scale applications is illustrated. A tallcone bottom treatment tank 11 of depth 9 is installed in sandy soil 10by either full excavation or by mixing polymer in the sand in situ andthan pumping out said sand while the tank settles in place and is filledwith water for ballast. This method is typically used for large powerpole concrete footings by Florida Power Corporation. A main flow pipe 14carries water to be treated to the vessel bottom 15. A side stream pipe13 carries ozone-laden water to pipe discharge 16 where the ozone-ladenwater mixes with mainstream water. Water progresses up the tankvertically at a slow rate, allowing for necessary contact time fordesired level of oxidation by ozone to the surface 17, whereat it isdischarged out the nozzle 18 for nutrient removal downstream. Anyprecipitates failing to the bottom of tank 11 are evacuated by sedimentline 12.

FIG. 2 illustrates an embodiment of the method of the present invention.A lake or other water body 20 from which water is drawn and supplied toan ozone treatment system 21 as depicted in FIG. 1. Chemicalflocculation or ultraviolet treatment systems 25 may be used topre-treat water to be ozone exposed to enhance ozone treatment. Ozonatedwater is then fed to a plant uptake system such as a periphyton filter22 or other aquatic plant system. If it is necessary to treat the waterfurther, the process can be repeated in a second ozone system 23 and asecond periphyton filter 24 before returning the treated water to thelake or water body 20.

Although only a few embodiments of the present invention have beendescribed in detail hereinabove, all improvements and modifications tothis invention within the scope or equivalents of the claims areincluded as part of this invention.

Having now described the invention, the construction, the operation anduse of preferred embodiments thereof, and the advantageous new anduseful results obtained thereby, the new and useful constructions, andreasonable equivalents thereof obvious to those skilled in the art, areset forth in the appended claims.

1. A method of treating water comprising the steps of: (a) directinginfluent comprising water desired to be treated from a body of waterinto a covered storage vessel; (b) exposing the influent in the coveredstorage vessel to ozone in sufficient quantity to disrupt cell walls ofundesired microorganisms therein, thereby releasing nutrients fromwithin the microorganisms in a form amenable to bioassimilation, theozone further in sufficient quantity to oxidize toxic, humic substancesto a form amenable to plant bioassimilation; (c) contacting aquaticplants with the ozone-exposed water, the aquatic plants adapted toremove the released and oxidized nutrients therefrom; and (d) returningwater emerging from the aquatic plants to the body of water.
 2. Themethod recited in claim 1, further comprising the step, prior to step(b), of pretreating the influent with a chemical flocculant toprecipitate out at least a portion of the excess nutrients.
 3. Themethod recited in claim 1, further comprising the step, prior to step(b), of generating ozone by at least one of exposing air to ultravioletradiation and creating a corona discharge.
 4. The method recited inclaim 1, further comprising the step of passing the water through anactivated carbon filter following step (c) and prior to step (d).
 5. Asystem for treating water comprising: first means for exposing waterdesired to be treated to ozone in sufficient quantity to disrupt cellwalls of undesired microorganisms therein, thereby releasing nutrientsfrom within the microorganisms in a form amenable to bioassimilation,the ozone further in sufficient quantity to oxidize toxic, humicsubstances to a form amenable to plant bioassimilation; first means fordirecting the water to be treated from a body of water to the firstozone-exposing means; aquatic plants adapted to remove the releasednutrients and the oxidized compounds from the ozone-exposed water;second means for directing the ozone-exposed water from thewater-exposing means to the aquatic plants; and third means fordirecting water emerging from the aquatic plants to the body of water.second means for exposing influent comprising water desired to betreated to ozone in sufficient quantity to further purify the water. 6.The system recited in claim 5, wherein the first exposing meanscomprises: a vessel; an influent line for transporting the influentadjacent a bottom of the vessel; an ozone line for injecting ozonatedwater adjacent the vessel bottom, for permitting the influent and theozonated water to mix while flowing upward in the vessel, therebyforming ozone-exposed water, and wherein: the second means for directingthe ozone-exposed water comprises means for transporting water fromadjacent a top of the vessel to the aquatic plants.
 7. The systemrecited in claim 5, further comprising means for pretreating theinfluent with a chemical flocculant to precipitate out at least some ofthe excess nutrients prior to exposing the influent to ozone in thefirst exposing means.
 8. The system recited in claim 7, wherein thefirst exposing means comprises a vessel, and the pretreating means ispositioned in the vessel, and further comprising means for removingprecipitate from a bottom of the vessel.
 9. The system recited in claim5, further comprising an activated carbon filter and means for passingthe water through the filter downstream of the aquatic plants andupstream of the third water-directing means.